Adjusting device of a chair backrest

Abstract

An adjusting device of a chair backrest includes a movable base, a connecting block and a positioning unit. The movable base encompasses an adjusting opening having plural continuous V-shaped grooves in two vertical sidewalls, a stopping groove and a projecting-downward portion, and two sliding rails. The connecting block is fitted in the movable base, possessing a rectangular recess. The positioning unit is installed in the rectangular recess, having two upholding feet fixed with the connecting block and respectively having a locking projection and a locking groove corresponding to each other. A spring is put between the upholding feet to elastically expand them. With the movable base fixed with the backrest and the connecting block fixed with a connecting rod, the movable base can be moved up and down together with the backrest, with the height of the backrest adjusted.

1. An adjusting device of a chair backrest, said adjusting device comprising:
 a movable base provided with an adjusting opening in a front wall, said adjusting opening having plural continual V-shaped grooves in two vertical sidewalls respectively, a bottom portion of said adjusting opening formed with a stopping groove and a top end of said adjusting opening formed with a projecting-downward portion, said movable base further having a sliding rail formed in two sides respectively; 
 a connecting block fitted in said movable base and provided with a side wing formed at two vertical sides respectively for plugging inside said sliding rail of said movable base, a rectangular recess formed in a front wall of said connecting block and provided with a projection on an intermediate portion and a through hole bored below said projection; and 
 a positioning unit assembled within said rectangular recess of said connecting block and provided with two upholding feet respectively bored with a pivotal hole, a pivotal pin used to be inserted through said pivotal holes of said upholding feet and said through hole of said connecting block and then fixed with a washer by pressing so as to keep said positioning unit jointed with said connecting block, one of said upholding feet provided with a locking projection corresponding to a locking groove provided in another said upholding foot, a spring installed between an inner wall of said upholding feet to expand said upholding feet to fit in one of plural pairs of said V-shaped grooves of said adjusting opening of said movable base. 
 
     
     
       2. The adjusting device of a chair backrest as claimed in  claim 1 , wherein one of said sliding rails of said movable base is provided with a long blocking wall vertically projected from its inner end, and an inner wall is formed to extend sidewise in parallel to said front wall from each of said sliding rails. 
     
     
       3. The adjusting device of a chair backrest as claimed in  claim 1 , wherein one of said side wings has a long projecting ridge, and at least a circular notch is cut at one side of said connecting block and provided with a locking projection formed on its inner wall, and a side wall is formed at two sides of said connecting block respectively. 
     
     
       4. The adjusting device of a chair backrest as claimed in  claim 3 , wherein a stabilizing ring made of plastics is inserted in said notch of said connecting block and provided with a slot. 
     
     
       5. An adjusting device of a seat back, said adjusting device comprising:
 a movable base provided with an adjusting opening in a front wall, said adjusting opening having plural continuous V-shaped grooves in two vertical sidewalls respectively, a bottom portion of said adjusting opening formed with a stopping groove, a top end of said adjusting opening formed with a projecting-downward portion, a sliding rail formed in two sides of said movable base respectively; 
 a connecting rod of a chair fitted in said movable base and provided with a side wing formed at its two sides respectively for plugging inside said sliding rail of said movable base, a rectangular recess formed in a front wall of said connecting rod and provided with a projection on an intermediate portion and a through hole bored below said projection; and 
 a positioning unit assembled within said rectangular recess of said connecting rod and provided with two upholding feet respectively bored with a pivotal hole, a pivotal pin used to be inserted through said pivotal holes of said upholding feet and said through hole of said connecting rod and then fixed with a washer by pressing so as to keep said positioning unit jointed with said connecting rod, one of said upholding feet provided with a locking projection corresponding to a locking groove provided in another said upholding foot, a spring installed between an inner wall of said upholding feet to expand said upholding feet wide. 
 
     
     
       6. The adjusting device of a seat back as claimed in  claim 5 , wherein each of said upholding feet of said positioning unit is provided with a spring groove formed in its inner wall. 
     
     
       7. The adjusting device of a seat back as claimed in  claim 5 , wherein one of said sliding rails of said movable base is provided with a long blocking ridge vertically projected from its inner end, and an inner wall is formed to extend sidewise in parallel to said front wall from each of said sliding rails. 
     
     
       8. The adjusting device of a seat back as claimed in  claim 5 , wherein one of said side wings has a long projection ridge, and at least a circular notch is cut at one side of said connecting rod and provided with a locking projection formed on its inner wall, and a side wall is formed at two sides of said connecting rod respectively. 
     
     
       9. The adjusting device of a seat back as claimed in  claim 8 , wherein a stabilizing ring made of plastics is inserted in said notch of said connecting rod and provided with a slot.